TWI640608B - Liquid-crystalline medium, processes and uses of the same and electro-optical display - Google Patents

Abstract

The invention relates to a liquid crystal medium with negative dielectric anisotropy, which comprises at least one compound of formula I Among them, R ¹ , R ^{1 *,} and a have the meanings indicated in claim 1, and are related to the use of the medium for an active matrix display based in particular on a VA, PS-VA, PALC, FFS, or IPS effect.

Description

Liquid crystal medium, method and use thereof, and electro-optic display

The invention relates to a liquid crystal medium with negative dielectric anisotropy, which comprises at least one compound of formula I Wherein R ¹ and R ^{1 *} each independently represent an alkyl group having 1-6 C atoms, and a represents 0 or 1.

This type of medium can be used especially for electro-optic displays with active matrix addressing based on the ECB effect and for IPS (coplanar switching) displays or FFS (fringing field switching) displays.

The principle of electrically controlled birefringence, the ECB (electrically controlled birefringence) effect, or the DAP (deformation of alignment phase) effect was first described in 1971 (MFSchieckel and K. Fahren-schon, `` Deformation of nematic liquid crystals with vertical orientation in electrical fields ", Appl. Phys. Lett. 19 (1971), 3912). Later described in the papers of J.F. Kahn (Appl. Phys. Lett. 20 (1972), 1193) and G. Labrunie and J. Robert (J. Appl. Phys. 44 (1973), 4869).

Papers by J. Robert and F. Clerc (SID 80 Digest Techn. Papers (1980), 30), papers by J. Duchene (Displays 7 (1986), 3), and papers by H. Schad (SID 82 Digest Techn. Papers (1982), 244) shows that the liquid crystal phase must have a ratio of high elastic constants K ₃ / K ₁ , high optical anisotropy values Δn and Δε A dielectric anisotropy value of -0.5 makes it suitable for use in high information display elements based on the ECB effect. The electro-optical display element based on the ECB effect has a vertical edge alignment (VA technology = vertical alignment type). Dielectric negative liquid crystal media can also be used in displays that use the so-called IPS or FFS effect.

Except for IPS (Coplanar Switching) displays (eg Yeo, SD, Paper 15.3: "An LC Display for the TV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pages 758 and 759) In addition to the long-known TN (Twisted Nematic) displays, especially for TV applications, for example, the following modes of displays using the ECB effect (also known as VAN (Vertical Aligned Nematic) displays) have established themselves as One of the three most important modern LCDs: MVA (multi-quadrant vertical alignment type, for example: Yoshide, H. et al., Thesis 3.1: "MVA LCD for Notebook or Mobile PCs ...", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book I, pages 6-9 and Liu, CT et al., Thesis 15.1: "A 46-inch TFT-LCD HDTV Technology ...", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pages 750 to 753) mode, PVA (patterned vertical alignment type, for example: Kim, Sang Soo, paper 15.4: "Super PVA Sets New State-of-the-Art for LCD-TV ``, SID 2004 International Sy mposium, Digest of Technical Papers, XXXV, Book II, pp. 760 to 763) mode, ASV (advanced ultra-visual type, for example: Shigeta, Mitzuhiro and Fukuoka, Hirofumi, thesis 15.2: "Development of High Quality LCDTV", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Book II, pages 754 to 757). For example, in Souk, Jun, SID Seminar 2004, seminar M-6: "Recent Advances in LCD Technology", Seminar Lecture Notes, M-6 / 1 to M-6 / 26 and Miller, Ian, SID Seminar 2004, seminar M- 7: "LCD- Television ", Seminar Lecture Notes, M-7 / 1 to M-7 / 32 to compare these technologies in a general form. Although the response time of modern ECB displays has been significantly improved by addressing methods (eg: Kim, Hyeon Kyeong et al., Paper 9.1: "A 57-in. Wide UXGA TFT-LCD for HDTV Application", SID 2004 International Symposium, Digest of Technical Papers, XXXV, Volume I, pages 106 to 109), but the achievement of video compatibility response time (especially in terms of grayscale switching) is still an issue that has not yet been satisfactorily resolved.

The industrial application of this effect in electro-optical display elements requires LC phases that must meet a variety of requirements. Of particular importance here are the chemical and physical effects on moisture and air (such as thermal, infrared, visible and ultraviolet radiation, and DC and AC electric fields).

In addition, an industrially usable LC phase is required to have a liquid crystal mesophase and a low viscosity in a suitable temperature range.

The series of compounds having liquid crystal mesophases disclosed to date do not include a single compound that meets all of these requirements. Therefore, a mixture of 2 to 25 (preferably 3 to 18) compounds is usually prepared in order to obtain a substance that can be used as an LC phase. However, it is not possible to easily prepare the optimal phase in this way, as no liquid crystal material with significant negative dielectric anisotropy and sufficient long-term stability has been available to date.

Matrix liquid crystal displays (MLC displays) are known. Non-linear elements that can be used for individual switching of individual pixels are, for example, active elements (ie, transistors). The term "active matrix" is then used, where two types can be distinguished:

1. A MOS (metal oxide semiconductor) transistor on a silicon wafer as a substrate.

2. Thin film transistor (TFT) on a glass plate as a substrate.

In the case of type 1, the electro-optic effects used are usually dynamic scattering or guest-host effects. Using monocrystalline silicon as the substrate material will limit the size of the display, as even the module assemblies of the various components of the display will cause problems at the joints.

In the case of the better and more promising type 2, the electro-optic effect used is usually the TN effect should.

Two technologies are distinguished: TFTs containing compound semiconductors such as CdSe, or TFTs based on polycrystalline or amorphous silicon. The latter technology is being adopted globally intensively.

The TFT matrix is applied inside one glass plate of a display, and the other glass plate carries a transparent counter electrode on the inside. Compared with the size of the pixel electrode, the TFT is small and does not actually have an adverse effect on the image. This technology can also be extended to displays with full color capabilities, in which mosaics of red, green, and blue filters are arranged in such a way that the filter element is opposed to each switchable pixel.

The TFT displays disclosed so far are usually operated as a TN unit with a crossed polarizer in transmission and are backlit.

The term MLC display here includes any matrix display with integrated non-linear elements, that is, in addition to the active matrix, it also includes displays with passive elements such as rheostats or diodes (MIM = metal-insulator-metal).

This type of MLC display is particularly suitable for TV applications (such as pocket TVs) or high-information displays in automotive or aircraft construction. In addition to the problems of the angular dependence of the contrast and the response time, difficulties arise due to the insufficiently high specific resistance of the liquid crystal mixture in MLC displays [TOGASHI, S., SEKIGUCHI, K., TANABE, H., YAMAMOTO , E., SORIMACHI, K., TAJIMA, E., WATANABE, H., SHIMIZU, H., Proc.Eurodisplay 84, September 1984: A 210-288 Matrix LCD Controlled by Double Stage Diode Rings, page 141 And following pages, Paris; STROMER, M., Proc. Eurodisplay 84, September 1984: Design of Thin Film Transistors for Matrix Addressing of Television Liquid Crystal Displays, pages 145 and following, Paris]. As the resistance decreases, the contrast of the MLC display deteriorates. Since the specific resistance of a liquid crystal mixture is generally reduced over the life of an MLC display due to interaction with the internal surface of the display, high (initial) resistance is very important for displays that must have acceptable resistance values over a long period of operation important.

The disadvantages of the MLC-TN displays disclosed so far are that their contrast is relatively low, the viewing angle dependency is relatively high, and it is difficult to produce grayscales in these displays.

Therefore, there continues to be an urgent need for MLC displays with extremely high specific resistances, yet with a wide operating temperature range, short response time, and low threshold voltages (by which various grayscales can be produced).

Achieving short response times is especially important for TV applications. To this end, the dielectric neutral compounds used in ECB or VA applications are especially compounds of the formula: Where R ¹ = H or CH ₃ Because these compounds are distinguished by a particularly low rotational viscosity and excellent solubility.

In LCD TV applications, reliability issues often occur, such as image sticking, that is, if the display has been addressed for an extended period of time, a significant "burning-in" of the image will occur.

This problem often occurs only after extended operating time of the television. The reason is often regarded as long-term backlight exposure and increased operating temperature, which can lead to processes that are still unexplained in the display, such as the interaction between the alignment layer and the liquid crystal mixture. In the case of liquid crystal mixtures, the cause of the image sticking problem is considered to be, for example, the above-mentioned commonly used neutral alkenyl compounds.

The present invention is based on the purpose of providing liquid crystal mixtures, which are used in particular for monitors and TV applications based on the ECB effect or the IPS or FFS effect and which do not have the above-mentioned disadvantages or have only such reductions. In particular, it is important to ensure that monitors and TVs also operate at extremely high and very low temperatures with short response times and improved availability. Reliability characteristics, especially with no image sticking or significantly reduced image sticking after long-term operation.

Surprisingly, it has now been found that this purpose can be achieved if a nematic liquid crystal mixture comprising at least one compound of the formula I is used in such display elements. Wherein R ¹ and R ^{1 *} each independently represent an alkyl group having 1 to 6 C atoms, and a represents 0 or 1.

The use of compounds of formula I in VA mixtures is known, for example, from EP 0 474 062 B1, U.S. 6,066,268, JP H11-228966, JP H11-236567, EP 1 106 671 B1, U.S. 2005/0230661.

In contrast to the prior art, in addition to the absence of a neutral alkenyl compound, the concept of a negative dielectric anisotropic mixture according to the present invention is also distinguished by a short response time and good low temperature stability.

The invention therefore relates to a liquid crystal medium comprising at least one compound of the formula I.

The mixture according to the invention preferably exhibits a very wide nematic phase range (clear point 60 ℃, better 65 ℃, especially 70 ℃), extremely favorable capacitance threshold, relatively high retention value and excellent low temperature stability at the same time at -30 ℃ and -40 ℃, as well as extremely low rotational viscosity and short response time. In addition, the mixture according to the invention is also distinguished by the fact that, in addition to the improvement of the rotational viscosity γ ₁ , an increase in the elastic constant K ₃₃ of the improved response time is also observed, and the mixture of the invention exhibits improved reliability characteristics .

The following indicates some preferred embodiments of the mixture according to the invention:

a) R ¹ and R ^{1 * in} Formula I represent a linear alkyl group, especially C ₂ H ₅ , nC ₃ H ₇ , nC ₄ H ₉ , and furthermore nC ₅ H ₁₁ , nC ₆ H ₁₃ . Particularly preferably, R ¹ represents nC ₃ H ₇ and R ^{1 *} represents CH ₃ , C ₂ H ₅ or nC ₃ H ₇ .

b) a liquid crystal medium comprising one, two, three, four or more, preferably one, two or three compounds of formula I.

c) a liquid crystal medium, wherein the proportion of the compound of formula I in the entire mixture is 3% by weight, preferably 10% by weight, especially preferred 15% by weight. Particularly preferred is a liquid crystal medium comprising one or more compounds of formula I in the range of 3% to 50%, preferably 25% to 35%. The compound of formula I with a = 0 is preferably present in the mixture in an amount of 15% to 35%. The compound of formula I with a = 1 is preferably present in the mixture in an amount of 3% to 30%.

d) Preferred compounds of formula I are compounds of formulae I-1 to I-6:

The mixture according to the invention preferably comprises a compound of formula I-1 and / or I-2 in an amount of preferably 5% to 30%.

The medium according to the invention particularly preferably comprises a tricyclic compound of the formula I-1 and / or a formula I-2 in combination with one or more bicyclic compounds of the formula I-3 to I-6. With one or more selected from the formulae I-3 to I- The total ratio of the compound of the formula I-1 and / or the compound of the formula I-2 of the compound combination of the bicyclic compound of 6 is preferably 5% to 40%, particularly preferably 15% to 35%.

Particularly preferred mixtures include compounds I-1 and I-3:

Compounds I-1 and I-3 are preferably present in the mixture at a concentration of 15% to 35%, particularly preferably 15% to 25% and particularly preferably 18% to 22% based on the entire mixture.

Particularly preferred mixtures include compounds I-2 and I-3:

Compounds I-2 and I-3 are preferably present in the mixture at a concentration of 15% to 35%, particularly preferably 15% to 25% and particularly preferably 18% to 22% based on the entire mixture.

Particularly preferred mixtures include the following three compounds:

The compounds I-1, I-2 and I-3 are preferably present in the mixture in a concentration of 15% to 35%, particularly preferably 15% to 25% and particularly preferably 18% to 22%.

e) a liquid crystal medium, further comprising one or more compounds selected from the group of compounds of formula IIA, IIB and IIC:

Wherein R ^2A , R ^2B and R ^2C each independently represent H, an alkyl group having up to 15 C atoms, which is unsubstituted, mono-substituted by CN or CF ₃ or mono-substituted by at least halogen, and wherein, these one or more of the groups CH ₂ group can be -O -, - S-, ,, -C≡C-, -CF ₂ O-, -OCF _2- , -OC-O- or -O-CO- are replaced in such a way that O atoms are not directly connected to each other, and L ^1-4 are each independently represented F or Cl, Z ² and Z ^{2 '} each independently represent a single bond, -CH ₂ CH _2- , -CH = CH-, -CF ₂ O-, -OCF _2- , -CH ₂ O-, -OCH _2- , -COO-, -OCO-, -C ₂ F _4- , -CF = CF-, -CH = CHCH ₂ O-, p is 1 or 2, q is 0 or 1, and v is 1 to 6 .

In the compounds of the formulae IIA and IIB, Z ² may have the same or different meanings. In the compound of formula IIB, Z ² and Z ^{2 ′} may have the same or different meanings.

In the compounds of the formulae IIA, IIB and IIC, R ^2A , R ^2B and R ^2C each preferably represent an alkyl group having 1 to 6 C atoms, especially CH ₃ , C ₂ H ₅ , nC ₃ H ₇ , nC ₄ H ₉ and nC ₅ H ₁₁ .

In the compounds of formula IIA and IIB, L ¹ , L ² , L ³ and L ⁴ preferably represent L ¹ = L ² = F and L ³ = L ⁴ = F, and furthermore, L ¹ = F and L ² = Cl, L ¹ = Cl and L ² = F, L ³ = F and L ⁴ = Cl, L ³ = Cl and L ⁴ = F. Z ² and Z ^{2 ′} in formulae IIA and IIB each preferably represent a single bond independently of each other, and further represent a -C ₂ H ₄ -bridge.

If Z ² = -C ₂ H ₄ -in Formula IIB, then Z ^{2 'is} preferably a single bond or if Z ^2' = -C ₂ H _4- , then Z ^{2 is} preferably a single bond. Among the compounds of the formulae IIA and IIB, (O) C _v H _{2v + 1} preferably represents OC _v H _{2v + 1} and further represents C _v H _{2v + 1} . In the compound of formula IIC, (O) C _v H _{2v + 1} preferably represents C _v H _{2v + 1} . In the compound of formula IIC, L ³ and L ⁴ each preferably represent F.

The following indicates the preferred compounds of Formula IIA, IIB and IIC:

Wherein the alkyl (alkyl) and alkyl ^* (alkyl ^*) independently of one another each represent a linear alkyl group having 1-6 C atoms.

Particularly preferred mixtures according to the invention comprise one or more of the formulae IIA-2, IIA-8, IIA-14, IIA-29, IIA-35, IIB-2, IIB-11, IIB-16 and IIC-1 Compound.

The proportion of the compound of the formula IIA and / or IIB in the entire mixture is preferably at least 20% by weight.

A particularly preferred medium according to the invention comprises a compound of formula IIC-1 Wherein alkyl and alkyl ^* have the meanings indicated above, their amounts are preferably> 3% by weight, especially> 5% by weight and particularly preferably 5% to 25% by weight.

f) a liquid crystal medium, further comprising one or more compounds of formula III Wherein R ³¹ and R ³² each independently represent a linear alkyl group, an alkoxyalkyl group or an alkoxy group having up to 12 C atoms, and Express , , , or , Z ³ represents a single bond, -CH ₂ CH _2- , -CH = CH-, -CF ₂ O-, -OCF _2- , -CH ₂ O-, -OCH _2- , -COO-, -OCO-, -C ₂ F _4- , -C ₄ H _8- , -CF = CF-.

The following indicates preferred compounds of formula III:

Wherein alkyl and alkyl ^* each independently represent a straight-chain alkyl group having 1-6 C atoms.

The medium according to the invention preferably comprises at least one compound of formula IIIa and / or formula IIIb.

The proportion of the compound of formula III in the entire mixture is preferably at least 5 weight%.

g) a liquid crystal medium, which additionally contains a total of preferably <20% by weight, especially <10% by weight of a compound of the formula: And / or And / or

Further, a mixture containing the following compounds according to the present invention is preferred.

h) a liquid crystal medium, further comprising one or more tetracyclic compounds of the formula

Wherein R ^7-10 each independently of one another have one of the meanings indicated ^2A of R, R ^2A represents H, an alkenyl group, an alkyl group having up to 15 C atoms, which is based unsubstituted, _{monosubstituted} by CN or CF Or at least mono-substituted with halogen, and wherein one or more of the CH ₂ groups of these groups may be -O-, -S-, , -C≡C-, -CF ₂ O-, -OCF _2- , -OC-O- or -O-CO- are replaced in such a way that O atoms are not directly connected to each other, and w and x each independently represent 1 To 6.

i) a liquid crystal medium, further comprising one or more compounds of formula Y-1 to Y-6:

Wherein R ¹⁴ to R ¹⁹ each independently represent an alkyl or alkoxy group having 1 to 6 C atoms; z and m each independently represent 1 to 6; x represents 0, 1, 2 or 3.

It is particularly preferred that the medium according to the invention comprises one or more 5% by weight of the compound of formula Y-1.

j) a liquid crystal medium, further comprising one or more fluorinated biphenyls of the formula T-1 to T-20:

Wherein R represents a linear alkyl or alkoxy group having 1 to 7 C atoms, and m is 1-6.

R preferably represents methyl, ethyl, propyl, butyl, pentyl, hexyl, methoxy, ethoxy, propoxy, butoxy, pentoxy.

The medium according to the invention preferably comprises bitriphenyls of the formulae T-1 to T-22 in an amount of 2-30% by weight, especially 5-20% by weight.

Particularly preferred are compounds of the formulae T-1, T-2 and T-20. Among these compounds, R preferably represents an alkyl group, and further represents an alkoxy group, each of which has 1-5 C atoms.

If the △ n value of the mixture 0.1, then bitriphenyl is preferably used in the mixture according to the invention. The preferred mixture comprises 2 to 20% by weight of one or more terphenyl compounds selected from the group of compounds T-1 to T20.

k) a liquid crystal medium, further comprising one or more biphenyls of formulas B-1 to B-3:

Wherein alkyl and alkyl ^* each independently represent a straight-chain alkyl group having 1-6 C atoms, and

The proportion of biphenyls of the formulae B-1 to B-3 in the entire mixture is preferably at least 3% by weight, especially 5 wt%.

Among the compounds of the formulae B-1 to B-3, the compound of the formula B-2 is particularly preferable.

Especially preferred biphenyls are

Wherein alkyl ^* represents an alkyl group having 1 to 6 C atoms. The medium according to the invention particularly preferably comprises one or more compounds of the formula B-1a and / or B-2c.

l) a liquid crystal medium comprising at least one compound of formulas Z-1 to Z-7:

Wherein R and alkyl have the meanings indicated above.

m) a liquid crystal medium comprising at least one compound of the formulae O-1 to O-18:

Wherein R ¹ and R ² have the meanings indicated with respect to R ^2A . R ¹ and R ² each preferably independently represent a linear alkyl group.

Preferred media include one or more formulas O-1, O-3, O-4, O-9, O-13, O-14, O-15, O-16, O-17 and / or O-18 Of compounds.

n) A preferred liquid crystal medium according to the present invention comprises one or more substances containing tetrahydronaphthyl or naphthyl units such as compounds of formulas N-1 to N-5:

Wherein R ^1N and R ^2N each independently have the meaning indicated by R ^2A , preferably represents a linear alkyl group, a linear alkoxy group, or a linear alkenyl group, and Z ¹ and Z ² each independently represent − C ₂ H _4- , -CH = CH-,-(CH ₂ ) ₄ -,-(CH ₂ ) ₃ O-, -O (CH ₂ ) _3- , -CH = CHCH ₂ CH _2- , -CH ₂ CH ₂ CH = CH-, -CH ₂ O-, -OCH _2- , -COO-, -OCO-, -C ₂ F _4- , -CF = CF-, -CF = CH-, -CH = CF- , -CF ₂ O-, -OCF _2- , -CH _2- , or a single bond.

o) Preferred mixtures include one or more difluorodibenzochroman compounds of formula BC, chroman of formula CR, phenanthrene fluoride of formulas PH-1 and PH-2, fluorinated diphenyl of formula BF Compounds of the benzofuran group:

Among them, R ^B1 , R ^B2 , R ^CR1 , R ^CR2 , R ¹ , and R ² each independently have the meaning of R ^2A . c is 0, 1, or 2.

The mixture according to the invention preferably comprises compounds of the formula BC, CR, PH-1, PH-2 and / or BF in an amount of 3 to 20% by weight, especially 3 to 15% by weight. Particularly preferred compounds of the formulae BC and CR are compounds BC-1 to BC-7 and compounds CR-1 to CR-5:

Wherein: Alkyl and alkyl ^* each independently represent a linear alkyl group having 1-6 C atoms, and alkenyl and alkenyl ^* each independently represent a linear alkenyl group having 2-6 C atoms .

Especially preferred is a mixture comprising one, two or three compounds of formula BC-2.

p) Preferred mixtures include one or more indan compounds of formula In

Among them, R ¹¹ , R ¹² , and each independently represent a straight-chain alkyl group, R ¹³ alkoxy group, alkoxyalkyl group, or alkenyl group having 1-6 C atoms, and R ¹² and R ¹³ additionally represent halogen, preferably Is F, Express i means 0, 1, or 2.

Preferred compounds of formula In are compounds of formulas In-1 to In-16 indicated below:

Particularly preferred are compounds of the formulae In-1, In-2 and In-3.

Compounds of formula In and sub-formulas In-1 to In-16 are preferably Concentrations of 5% by weight, in particular 5% to 30% by weight and particularly preferably 5% to 25% by weight, are used in the mixtures according to the invention.

q) The preferred mixture further comprises one or more compounds of formula L-1 to L-11:

Wherein R, R ¹ and R ² independently of one another have the meanings indicated in each of R ^2A, R ^2A represents H, an alkenyl group, an alkyl group having up to 15 C atoms, which is based unsubstituted, CN or CF ₃ Mono-substituted or at least mono-substituted by halogen, and wherein one or more of these groups CH ₂ groups may be -O-, -S-, , -C≡C-, -CF ₂ O-, -OCF _2- , -OC-O- or -O-CO- are replaced in such a way that O atoms are not directly connected to each other, and the alkyl group has 1-6 C Atomic alkyl. s represents 1 or 2.

Particularly preferred are compounds of formulas L-1 and L-4, especially compounds of L-4.

The compounds of the formulae L-1 to L-11 are preferably used at a concentration of 5 to 50% by weight, especially 5 to 40% by weight and particularly preferably 10 to 40% by weight.

The following indicates particularly preferred embodiments.

The medium according to the invention comprises at least three compounds selected from the group of compounds of the formulae I-1 to I-6 in an amount of preferably from 8 to 50% by weight:

A medium according to the invention comprises one or more of the following formulas And / or And / or And / or

Compound of formula I-1 and / or I-2:

The following indicates the concept of particularly preferred mixtures: (The abbreviations used are described in Table A. Here n and m each independently represent 1-6.)

The mixture according to the invention preferably comprises-CPY-n-Om, preferably CPY-2-O2, CPY-3-O2 and / or CPY-, based on the entire mixture, preferably at a concentration of> 5%, especially 10% to 30%. 5-O2, and / or-preferably CY-n-Om at a concentration of> 5%, especially 15% to 50% based on the entire mixture, more preferably CY-3-O2, CY-3-O4, CY-5- O2 and / or CY-5-O4, and / or-CCY-n-Om, preferably at a concentration of> 5%, especially 10% to 30%, more preferably CCY-4-O2, CCY-3- O2, CCY-3-O3 and / or CCY-5-O2, and / or-preferably CLY-n-Om at a concentration of> 5%, especially 10% to 30%, more preferably CLY-2- O4, CLY-3-O2 and / or CLY-3-O3, and / or-based on the entire mixture, preferably CK-nF at a concentration of> 5%, especially 5% to 25%, more preferably CK-3-F, CK-4-F and / or CK-5-F, wherein the proportion of all mesogen compounds in the liquid crystal mixture according to the present invention is 100%.

In addition, preferred are mixtures according to the invention that include the following mixture concepts: (n and m each independently represent 1-6.)

-CPY-n-Om and CY-n-Om at a concentration of preferably 10% to 80% based on the entire mixture, and / or-CPY-n-Om and CK-nF at a concentration of 10% to 70% based on the entire mixture, preferably , And / or-CPY-n-Om and CK-nF and CLY-n-Om with a concentration of preferably 10% to 80% based on the entire mixture, wherein the proportion of all the mesogen compounds in the liquid crystal mixture according to the present invention is 100%.

In addition, the present invention also relates to an electro-optic display with active matrix addressing based on the ECB, IPS, or FFS effect, which is characterized in that it contains a liquid crystal medium as in any one of claims 1 to 26 as a dielectric.

The liquid crystal medium according to the present invention preferably has -20 ° C to 70 ° C, especially preferred -30 ° C to 80 ℃, especially preferred since -40 ° C to Nematic phase at 90 ° C.

The term "having a nematic phase" here means that on the one hand, no smectic phase and crystal are observed at a corresponding temperature and low temperature, and on the other hand, if the nematic phase is heated, it does not become clear. The research at low temperature was carried out at a corresponding temperature in a flow viscometer and checked by storing in a test unit with a layer thickness corresponding to electro-optical applications for at least 100 hours. If the storage stability at -20 ° C in the corresponding test unit is 1000h or more, the medium is considered to be stable at this temperature. At temperatures of -30 ° C and -40 ° C, the corresponding times are 500h and 250h, respectively. At high temperatures, the clear point is measured in a capillary tube by conventional methods.

The liquid crystal mixture preferably has a nematic phase range of at least 60K and at most 30mm ² at 20 ° C. Flow viscosity ν _{20 of} s ^-1 .

The birefringence value Δn in the liquid crystal mixture is usually between 0.07 and 0.16, preferably between 0.08 and 0.12.

The liquid crystal mixture according to the present invention has a Δε of about -0.5 to -8.0, especially -3.0 to -6.0, where Δε represents dielectric anisotropy. The rotational viscosity γ ₁ is preferably at 20 ° C. 165mPa. s, especially 140mPa. s.

The liquid crystal medium according to the present invention has a relatively low threshold voltage value (V ₀ ). It is preferably in the range of 1.7V to 3.0V, and particularly preferably 2.75V and especially preferred 2.4V.

For the present invention, the term "threshold voltage" is related to a capacitance threshold (V ₀ ), and is also referred to as a Freedericks threshold, unless explicitly indicated otherwise.

In addition, the liquid crystal medium according to the present invention has a high voltage holding ratio value in a liquid crystal cell, especially after the display backlight is exposed.

Generally, liquid crystal media with a low addressing voltage or threshold voltage exhibit a lower voltage retention than those with a higher addressing voltage or threshold voltage, and vice versa.

For the present invention, the term "dielectrically positive compound" means a compound with Δε> 1.5, and the term "dielectrically neutral compound" means -1.5 △ ε 1.5 compounds, and the term "dielectric negative compound" means compounds with Δε <-1.5. The dielectric anisotropy of the compound is determined here by dissolving 10% of the compound in the liquid crystal host and measuring the capacitance of the resulting mixture in at least one test cell. In each case, the layer thickness is 20 μm and verticality occurs at 1 kHz. And parallel surface alignment. The measurement voltage is usually 0.5V to 1.0V, but it is always lower than the capacitance threshold of the respective liquid crystal mixture under study.

All temperature values indicated in the present invention are in ° C.

The mixture according to the invention is suitable for all VA-TFT applications, such as VAN, MVA, (S) -PVA and ASV. In addition, the mixture according to the invention is also suitable for IPS (coplanar switching type) and FFS (fringing field switching type) applications where Δε is negative.

The nematic liquid crystal mixture in a display according to the present invention usually contains two components A and B, which are themselves composed of one or more individual compounds.

Component A has significant negative dielectric anisotropy and provides dielectric anisotropy -0.5 nematic phase. In addition to one or more compounds of formula I, component A also preferably comprises compounds of formula IIA, IIB and / or IIC, and also compounds of formula III.

The proportion of component A is preferably between 45% and 100%, especially between 60% and 100%.

For component A, it is better to choose the value of △ ε One (or more) individual compounds at -0.8. The smaller the proportion of A in the entire mixture, the more negative this value must be.

Component B has significant nematogeneity and has a flow viscosity of no more than 30 mm ² at 20 ° C. s ^-1 , preferably not more than 25mm ² . s ^-1 .

A particularly preferred individual compound in component B is a flow viscosity of no more than 18 mm ² at 20 ° C. s ^-1 , preferably no more than 12mm ² . Very low viscosity nematic liquid crystal of s ^-1 .

Component B is monomorphic or tautomeric nematic, does not have a smectic phase, and can prevent the smectic phase from appearing in the liquid crystal mixture at low to very low temperatures. For example, if various highly nematic substances are added to the smectic liquid crystal mixture, the nematicity of these substances can be compared by the degree of inhibition of the obtained smectic phase.

Those skilled in the art know many suitable substances from the literature. Particularly preferred are compounds of formula III.

In addition, these liquid crystal phases may also contain more than 18 components, preferably 18 to 25 components.

In addition to one or more compounds of formula I, these phases also preferably contain 4 to 15, especially 5 to 12, and particularly preferably <10 compounds of formula IIA, IIB and / or IIC and optionally Compound of Formula III.

In addition to the compounds of the formula I and the compounds of the formula IIA, IIB and / or IIC and optionally the compounds of the formula III, other ingredients can also be, for example, up to 45% of the entire mixture, but preferably up to 35%, especially more Up to 10%.

Other ingredients are preferably selected from nematic or nematic base materials (especially known materials) from the following categories: oxazobenzene, benzylidene aniline, biphenyl, bitriphenyl, phenyl benzoate or benzoic acid Cyclohexyl, phenyl cyclohexylcarboxylate or cyclohexylcarboxylate, phenylcyclohexane, cyclohexylbiphenyl, cyclohexylcyclohexane, cyclohexylnaphthalene, 1,4-dicyclohexylbiphenyl or ring Hexylpyrimidine, phenyl- or cyclohexyldioxane, optionally halogenated stilbene, benzylphenyl ether, diphenylacetylene, and substituted cinnamate.

The most important compound suitable as a component of this type of liquid crystal phase is characterized by having the formula IV R ²⁰ -LGER ²¹ IV

Wherein L and E each represent a system derived from 1,4-disubstituted benzene and cyclohexane ring, 4,4'-disubstituted biphenyl, phenylcyclohexane and cyclohexylcyclohexane system, and 2,5-disubstituted Carbocyclic or heterocyclic ring systems of pyrimidine and 1,3-dioxane ring, 2,6-disubstituted naphthalene, dihydronaphthalene and tetrahydronaphthalene, quinazoline and tetrahydroquinazoline.

G represents -CH = CH-, -N (O) = N-, -CH = CQ-, -CH = N (O)-, -C≡C-, -CH ₂ -CH _2- , -CO-O -, -CH ₂ -O-, -CO-S-, -CH ₂ -S-, -CH = N-, -COO-Phe-COO-, -CF ₂ O-, -CF = CF-, -OCF _2- , -OCH ₂ -,-(CH ₂ ) ₄ -,-(CH ₂ ) ₃ O-, or CC single bond, Q represents halogen, preferably chlorine, or -CN, and each of R ²⁰ and R ²¹ Means an alkyl, alkenyl, alkoxy, alkoxyalkyl or alkoxycarbonyloxy group with up to 18, preferably up to 8 carbon atoms, or one of these groups means CN, NC , NO ₂ , NCS, CF ₃ , SF ₅ , OCF ₃ , F, Cl or Br.

In most of these compounds, R ²⁰ and R ²¹ are different from each other, and one of these groups is usually an alkyl group or an alkoxy group. Other variations of the proposed substituents are also commonly used. Many of these substances or mixtures thereof are commercially available. All of these materials can be prepared by methods known from the literature.

It is self-evident to those skilled in the art that the VA, IPS or FFS mixture according to the present invention may also include, for example, compounds in which H, N, O, Cl and F have been replaced by corresponding isotopes.

In addition, a polymerizable compound such as the so-called reactive mesogen disclosed in US 6,861,107 can also be added at a concentration of preferably 0.12 to 5% by weight, particularly preferably 0.2 to 2% by weight, based on the mixture to In the mixture according to the invention. These mixtures may optionally also contain initiators such as described in U.S. 6,781,665. An initiator (eg, Irganox-1076 from Ciba) is preferably added to the mixture containing a polymerizable compound in an amount of 0 to 1%. This type of mixture can be used in the so-called polymer-stabilized VA mode (PS-VA), in which the polymerization of the reactive mesogen is intended to occur in the liquid crystal mixture. A prerequisite for this polymerization is that the liquid crystal mixture itself does not contain any polymerizable components. Suitable polymerizable compounds are listed, for example, in Table D.

In addition, the mixture according to the present invention may also contain conventional additives such as stabilizers, antioxidants, UV sorbents, nano particles, particulates, and the like.

As described, for example, in EP-A 0 240 379, the construction of the liquid crystal display according to the invention conforms to ordinary geometry.

The following examples are intended to illustrate the invention in a non-limiting manner. Above and below, the percentage data represent weight percentages and all temperatures are indicated in degrees Celsius.

In addition to the compounds of the formula IIA and / or IIB and / or IIC, one or more compounds of the formula I, the mixture according to the invention preferably comprises one or more compounds from Table A indicated below.

Table A uses the following abbreviations: (n, m, z: each independently 1, 2, 3, 4, 5 or 6; (O) C _m H _{2m + 1} means OC _m H _{2m + 1} or C _m H _{2m + 1} )

The liquid crystal mixtures that can be used according to the invention are prepared in a manner that is known per se. In general, it is suitable to dissolve a required amount of a component used in a small amount at a high temperature in a component constituting a main component. May also be mixed in organic solvents (e.g. acetone, chloroform or methanol) Combine the solutions of the components and, for example, remove the solvent again by distillation after thorough mixing.

The liquid crystal phase according to the present invention can be modified by suitable additives in such a manner that it can be used for any type of, for example, ECB, VAN, IPS, GH, or ASM-VA LCD displays that have been disclosed so far.

The dielectric may also contain other additives known to those skilled in the art and described in the literature, such as UV absorbers, antioxidants, nano particles, and free radical scavengers. For example, 0 to 15% of polychromatic dyes, stabilizers, or palmar dopants can be added. Suitable stabilizers for the mixtures according to the invention are the stabilizers listed in particular in Table B.

For example, 0 to 15% of polychromic dyes can be added. In addition, conductive salts can be added, preferably 4-hexyloxybenzoic acid ethyl dimethyl dodecyl ammonium, tetraphenyl tetrahydroborate. Double salts of ammonium or crown ether (see, for example, Haller et al., Mol. Cryst. Liq. Cryst. Vol. 24 , pp. 249-258 (1973)) to improve conductivity or substances may be added to adjust the dielectric properties of the nematic phase Anisotropy, viscosity and / or alignment. Substances of this type are described, for example, in DE-A 22 09 127, 22 40 864, 23 21 632, 23 38 281, 24 50 088, 26 37 430 and 28 53 728.

Table B shows possible dopants that can be added to the mixture according to the invention. If the mixture contains a dopant, it is used in an amount of 0.01 to 4% by weight (preferably 0.1 to 1.0% by weight).

For example, it is shown in Table C below that it can be added to the mixture according to the invention in an amount of up to 10% by weight, preferably 0.01% to 6% by weight, especially 0.1% to 3% by weight, based on the total amount of the mixture. Stabilizer. Preferred stabilizers are especially BHT derivatives, such as 2,6-di-third-butyl-4-alkylphenol and Tinuvin 770.

Table C (n = 1-12)

Reactive mesogens suitable for the mixture according to the invention in PS-VA applications are shown in Table D below.

Table D

The following examples are intended to illustrate the invention in a non-limiting manner. Above and below, V ₀ represents the capacitive threshold voltage [V] at 20 ° C; Δn represents the optical anisotropy measured at 20 ° C and 589nm; Δε represents 20 ° C and 1kHz The dielectric anisotropy below; cl.p. represents the clear point [℃]; K ₁ represents the elastic constant at 20 ° C, and "splay" deformation [pN]; K ₃ represents the temperature at 20 ° C Elastic constant, "bend" deformation [pN]; γ ₁ represents the rotational viscosity [mPa. s]; LTS stands for low-temperature stability (nematic) measured in a test cell.

The display for threshold voltage measurement has two plane parallel outer plates with a distance of 20 μm and an electrode layer with an SE-1211 (Nissan Chemicals) overlay alignment layer on the inner side of the outer plate, which affects the vertical alignment of the liquid crystal.

Unless otherwise specifically indicated, all concentrations in this application are related to the corresponding mixture or mixture component. Unless otherwise specifically indicated, all physical properties are determined according to the description of "Merck Liquid Crystals, Physical Properties of Liquid Crystals" of the November 1997 version of Merck KGaA, Germany, and are suitable for temperatures of 20 ° C.

Mixture example

Example 1

Example 2

Example 3

Example 4

Example 5

Example 6

Example 7

Example 8

Example 9

Example 10

Example 11

Example 12

Example 13

Example 14

Example 15

Example 16

Example 17

Example 18

Example 19

Example 20

Example 21

Example 22

Example 23

99.8% of the mixture according to Example 1 was mixed with 0.2% of a polymerizable compound of the following formula to prepare a PS-VA mixture

Example 24

99.8% of the mixture according to Example 15 was mixed with 0.2% of a polymerizable compound of the following formula to prepare a PS-VA mixture

Claims (26)

A liquid crystal medium with negative dielectric anisotropy based on a mixture of polar compounds, characterized in that it contains at least one compound of formula I

Wherein: R ¹ and R ^{1 *} each independently represent an alkyl group having 1-6 C atoms, and a represents 0 or 1; based on the entire mixture, the content is less than 10% by weight of one or more formulas CC- nV compound

Where n is 3, 4 or 5; and based on the entire mixture, the content is 10 to 30% by weight of one or more compounds of the formula CPY-n-Om

Where n and m each independently represent an integer of 1 to 6. The liquid crystal medium according to claim 1, wherein in the formula CC-n-V, n is 3. The liquid crystal medium of claim 1, wherein the medium contains at least one compound of formulae I-1 to I-6:

The liquid crystal medium according to claim 3, wherein the medium contains at least one compound of formula I and the compound of formula I-1 and formula I-3 in an amount of 15 to 35% by weight based on the entire mixture. The liquid crystal medium according to claim 4, wherein the content of the compounds of formula I-1 and formula I-3 is 15 to 25% by weight based on the entire mixture. The liquid crystal medium according to claim 4, wherein the content of the compounds of formula I-1 and formula I-3 is 18 to 22% by weight based on the entire mixture. The liquid crystal medium according to claim 3, wherein the medium contains at least one compound of formula I and the compound of formula I-2 and formula I-3 in an amount of 15 to 35% by weight based on the entire mixture. The liquid crystal medium according to claim 7, wherein the content of the compounds of Formula I-2 and Formula I-3 is 15 to 25% by weight based on the entire mixture. The liquid crystal medium according to claim 7, wherein the content of the compounds of formula I-2 and formula I-3 is 18 to 22% by weight based on the entire mixture. The liquid crystal medium according to claim 3, wherein the medium contains at least one compound of formula I and the compound of formula I-1, formula I-2 and formula I-3 in an amount of 15 to 35% by weight based on the entire mixture. The liquid crystal medium according to claim 10, wherein the content of the compounds of Formula I-1, Formula I-2 and Formula I-3 is 15 to 25% by weight based on the entire mixture. The liquid crystal medium according to claim 10, wherein the content of the compounds of Formula I-1, Formula I-2 and Formula I-3 is 18 to 22% by weight based on the entire mixture. The liquid crystal medium of claim 3, wherein the medium contains a compound of formula I-3. The liquid crystal medium of claim 1, wherein the one or more compounds of formula CPY-n-Om include compounds of formula CPY-2-O2 or CPY-3-O2:

The liquid crystal medium according to any one of claims 1 to 14, wherein the medium further comprises one or more compounds of formulae IIA to IIC:

Where R ^2A , R ^2B and R ^2C each independently represent H, alkenyl, alkyl having up to 15 C atoms, which is unsubstituted, mono-substituted by CN or CF ₃ or at least mono-substituted by halogen, And among them, one or more of the CH ₂ groups may be -O-, -S-,

,, -C≡C-, -CF ₂ O-, -OCF _2- , -OC-O-, or -O-CO- are replaced in such a way that the O atoms are not directly connected to each other, and L ^1-4 are each independently expressed F or Cl, Z ² and Z ^{2 '} each independently represent a single bond, -CH ₂ CH _2- , -CH = CH-, -CF ₂ O-, -OCF _2- , -CH ₂ O-, -OCH _2- , -COO-, -OCO-, -C ₂ F _4- , -CF = CF-, -CH = CHCH ₂ O-, p represents 1 or 2, q represents 0 or 1, and v represents 1 to 6 ; But the one or more compounds of formula IIB do not include the one or more compounds of formula CPY-n-Om as described in claim 1. The liquid crystal medium according to any one of claims 1 to 14, wherein the medium further comprises one or more compounds of formula III

Wherein R ³¹ and R ³² each independently represent a linear alkyl group, an alkoxyalkyl group or an alkoxy group having up to 12 C atoms, and

Express

,

,

,

or

, Z ³ represents a single bond, -CH ₂ CH _2- , -CH = CH-, -CF ₂ O-, -OCF _2- , -CH ₂ O-, -OCH _2- , -COO-, -OCO-, -C ₂ F _4- , -C ₄ H ₉ -or -CF = CF-. The liquid crystal medium according to any one of claims 1 to 14, wherein the medium further comprises one or more biphenyls of formula B-1 to B-3:

Wherein alkyl and alkyl ^* each independently represent a linear alkyl group having 1-6 C atoms, and

The liquid crystal medium according to any one of claims 1 to 14, wherein the medium further comprises one or more terphenyls of formula T-1 to T-20:

Where R represents a linear alkyl or alkoxy group having 1-7 C atoms, and m represents 1-6. The liquid crystal medium according to any one of claims 1 to 14, wherein the medium additionally contains one or more compounds of formulae O-1 to O-18:

Wherein R ¹ and R ² each independently represent H, an alkyl group having up to 15 C atoms, which is unsubstituted, mono-substituted by CN or CF ₃ or at least mono-substituted by halogen, and wherein, such groups One or more CH ₂ groups in the group can be selected from -O-, -S-,

, -C≡C-, -CF ₂ O-, -OCF _2- , -OC-O- or -O-CO- are replaced in such a way that O atoms are not directly connected to each other. The liquid crystal medium according to any one of claims 1 to 14, wherein the medium further comprises one or more indan compounds of formula In:

among them

R ¹² and R ¹³ additionally represent halogen,

Express

i means 0, 1, or 2. The liquid crystal medium according to any one of claims 1 to 14, wherein the medium additionally contains one or more compounds of formulae Z-1 to Z-7:

Where R represents a linear alkyl or alkoxy group having 1-7 C atoms, and alkyl represents a linear alkyl group having 1-6 C atoms. The liquid crystal medium according to any one of claims 1 to 14, wherein the ratio of the at least one compound of formula I in the entire mixture is

3% by weight. A method for preparing a liquid crystal medium according to any one of claims 1 to 22, characterized in that at least one compound of formula I is mixed with at least one other liquid crystal compound, and additives are optionally added. A use of the liquid crystal medium according to any one of claims 1 to 22 in an electro-optic display. An electro-optical display with active matrix addressing, characterized in that it contains the liquid crystal medium according to any one of claims 1 to 22 as a dielectric substance. The electro-optic display according to claim 25, wherein it is a VA, PS-VA, PALC, FFS or IPS display.